由于某些類(lèi)型的固有的實(shí)現(xiàn)邏輯，使得它們具有兩個(gè)變化的維度，乃至多個(gè)緯度的變化。
如何應(yīng)對(duì)這種“多維度的變化”？如何利用面向?qū)ο蠹夹g(shù)來(lái)使得類(lèi)型可以輕松地沿著兩個(gè)乃至多個(gè)方向變化，而不引入額外的復(fù)雜度？

模式定義

將抽象部分(業(yè)務(wù)功能)與實(shí)現(xiàn)部分(平臺(tái)實(shí)現(xiàn))分離，使它們都可以獨(dú)立地變化。

結(jié)構(gòu)

在這里插入圖片描述

要點(diǎn)總結(jié)

Bridge模式使用“對(duì)象間的組合關(guān)系”解耦了抽象和實(shí)現(xiàn)之間固有的綁定關(guān)系，使得抽象和實(shí)現(xiàn)可以沿著各自的維度來(lái)變化。所謂抽象和實(shí)現(xiàn)沿著各自緯度的變化，即“子類(lèi)化”它們。
Bridge模式有時(shí)候類(lèi)似于多繼承方案，但是多繼承方案往往違背單一職責(zé)原則（即一個(gè)類(lèi)只有一個(gè)變化的原因），復(fù)用性比較差。Bridge模式是比多繼承方案更好的解決方法。
Bridge模式的應(yīng)用一般在“兩個(gè)非常強(qiáng)的變化維度”，有時(shí)一個(gè) 類(lèi)也有多于兩個(gè)的變化維度，這時(shí)可以使用Bridge的擴(kuò)展模式。

cpp

class Messager {
public:
    virtual void Login(string username, string password) = 0;
    virtual void SendMessage(string message) = 0;
    virtual void SendPicture(Image image) = 0;
    virtual void PlaySound() = 0;
    virtual void DrawShape() = 0;
    virtual void WriteText() = 0;
    virtual void Connect() = 0;
    virtual ~Messager() {}
};
//平臺(tái)實(shí)現(xiàn)
class PCMessagerBase : public Messager {
public:
    virtual void PlaySound() {
        //**********
    }
    virtual void DrawShape() {
        //**********
    }
    virtual void WriteText() {
        //**********
    }
    virtual void Connect() {
        //**********
    }
};
class MobileMessagerBase : public Messager {
public:
    virtual void PlaySound() {
        //==========
    }
    virtual void DrawShape() {
        //==========
    }
    virtual void WriteText() {
        //==========
    }
    virtual void Connect() {
        //==========
    }
};
//業(yè)務(wù)抽象
class PCMessagerLite : public PCMessagerBase {
public:
    virtual void Login(string username, string password) {
        PCMessagerBase::Connect();
        //........
    }
    virtual void SendMessage(string message) {
        PCMessagerBase::WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        PCMessagerBase::DrawShape();
        //........
    }
};
class PCMessagerPerfect : public PCMessagerBase {
public:
    virtual void Login(string username, string password) {
        PCMessagerBase::PlaySound();
        //********
        PCMessagerBase::Connect();
        //........
    }
    virtual void SendMessage(string message) {
        PCMessagerBase::PlaySound();
        //********
        PCMessagerBase::WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        PCMessagerBase::PlaySound();
        //********
        PCMessagerBase::DrawShape();
        //........
    }
};
class MobileMessagerLite : public MobileMessagerBase {
public:
    virtual void Login(string username, string password) {
        MobileMessagerBase::Connect();
        //........
    }
    virtual void SendMessage(string message) {
        MobileMessagerBase::WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        MobileMessagerBase::DrawShape();
        //........
    }
};
class MobileMessagerPerfect : public MobileMessagerBase {
public:
    virtual void Login(string username, string password) {
        MobileMessagerBase::PlaySound();
        //********
        MobileMessagerBase::Connect();
        //........
    }
    virtual void SendMessage(string message) {
        MobileMessagerBase::PlaySound();
        //********
        MobileMessagerBase::WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        MobileMessagerBase::PlaySound();
        //********
        MobileMessagerBase::DrawShape();
        //........
    }
};
void Process() {
    //編譯時(shí)裝配
    Messager* m = new MobileMessagerPerfect();
}

class Messager {
protected:
    MessagerImp* messagerImp;//...
public:
    virtual void Login(string username, string password) = 0;
    virtual void SendMessage(string message) = 0;
    virtual void SendPicture(Image image) = 0;
    virtual ~Messager() {}
};
class MessagerImp {
public:
    virtual void PlaySound() = 0;
    virtual void DrawShape() = 0;
    virtual void WriteText() = 0;
    virtual void Connect() = 0;
    virtual MessagerImp() {}
};
//平臺(tái)實(shí)現(xiàn) n
class PCMessagerImp : public MessagerImp {
public:
    virtual void PlaySound() {
        //**********
    }
    virtual void DrawShape() {
        //**********
    }
    virtual void WriteText() {
        //**********
    }
    virtual void Connect() {
        //**********
    }
};
class MobileMessagerImp : public MessagerImp {
public:
    virtual void PlaySound() {
        //==========
    }
    virtual void DrawShape() {
        //==========
    }
    virtual void WriteText() {
        //==========
    }
    virtual void Connect() {
        //==========
    }
};
//業(yè)務(wù)抽象 m
//類(lèi)的數(shù)目：1+n+m
class MessagerLite :public Messager {
public:
    virtual void Login(string username, string password) {
        messagerImp->Connect();
        //........
    }
    virtual void SendMessage(string message) {
        messagerImp->WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        messagerImp->DrawShape();
        //........
    }
};
class MessagerPerfect :public Messager {
public:
    virtual void Login(string username, string password) {
        messagerImp->PlaySound();
        //********
        messagerImp->Connect();
        //........
    }
    virtual void SendMessage(string message) {
        messagerImp->PlaySound();
        //********
        messagerImp->WriteText();
        //........
    }
    virtual void SendPicture(Image image) {
        messagerImp->PlaySound();
        //********
        messagerImp->DrawShape();
        //........
    }
};
void Process() {
    //運(yùn)行時(shí)裝配
    MessagerImp* mImp = new PCMessagerImp();
    Messager* m = new Messager(mImp);
}